It is known that when genetic material is introduced into a population of cells by means of transformation, only a number of the cells will be transformed successfully. After transformation the transformed cells must be identified and selected from a population of transformed and non-transformed cells. A selection gene is therefore generally also introduced into the cell for this purpose in addition to the desired transgene. The selection gene herein codes for instance for a property with which the genetically transformed cells can be identified. Examples of such selection genes are for instance genes which code for resistance to antibiotics or herbicides. After the transformation the population of transformed and non-transformed cells is brought into contact with the antibiotic or herbicide toxic for the non-transformed (“wild-type”) cells, so that only the transformed cells are able to survive and grow due to the presence of the introduced selection gene.
The use of such selection genes which code for antibiotic- or herbicide-resistance is however not generally desirable for transgenic crops which are introduced on a large scale into the environment, and particularly in food crops. Another drawback of such a selection mechanism is further for instance that the non-transformed cells will generally die off, and moreover that when the population of cells is a coherent tissue of cells or a whole organism, the transformed cells can also die as a result of for instance harmful compounds secreted by the dying, non-transformed cells.
The object of the present invention is to provide a method for selecting transformed cells from a population of transformed and non-transformed cells, wherein the above stated drawbacks are obviated.